Self-signup error on JSM open Portal

Issue Summary

When setting an open Portal on JSM, when trying to raise tickets through the Portal the below error message appears:

Couldn't send request
Sorry, self-signup is disabled for this help center. You need to be invited first.

The message appears due to an error on the Permission scheme of the project.

Steps to Reproduce

1. Setup an open Portal
2. On the Permission scheme, add the "Project Role: Service Desk Customers" to the "Edit Issues" permission
   
3. Try to raise a ticket on the open portal for the project

Expected Results

Users should be able to raise the requests on the Portal and create a new account.

Actual Results

The below error message appears, even with the open Portal set correctly:

Couldn't send request
Sorry, self-signup is disabled for this help center. You need to be invited first.

Workaround

Remove the "Project Role: Service Desk Customers" from the "Edit Issues" permission in the Permission scheme of the project.